11. P. Hartwrìghtii, Gray. Perennial, very closely allied to n. 9, growing usually in mud, the ascending stems rooting at base and very leafy, more or less rough-hairy, at least on the sheaths and bracts, the former ciliate and often with abruptly spreading foliaceous borders; leaves rather narrow (2–7´ long), on very short petioles; flowers and fruit as in n. 9.—N. Eng. and N. Y., to Minn., Iowa, and far westward. When growing in water the floating leaves are thicker and glabrous.
12. P. Càreyi, Olney. Annual, erect, the stem (3–5° high) and peduncles glandular-bristly; leaves narrowly lanceolate, attenuate to both ends, roughish; sheaths ciliate or sometimes margined; spikes slender, loose and nodding; flowers purplish; stamens mostly 5.—Shady swamps, S. Maine and N. H. to Penn. and Ont.
P. orientàle, L. (Prince's Feather.) Tall branching annual, soft-hairy; leaves ovate or oblong, pointed, distinctly petioled; sheaths ciliate or often with an abrupt spreading border; flowers large, bright rose-color, in dense cylindrical nodding spikes; stamens 7.—Sparingly escaped from gardens into waste grounds. (Adv. from India)
P. Persicària, L. (Lady's Thumb.) Nearly smooth and glabrous (12–18´ high); sheaths more or less bristly-ciliate; leaves lanceolate, pointed, roughish, often marked with a dark triangular or lunar spot near the middle; spikes ovoid or oblong, dense, erect, on smooth (or at least not glandular) peduncles; stamens mostly 6; styles half 2–3-cleft; achene gibbous-flattened or sometimes triangular, smooth and shining.—Waste and damp places, very common. (Nat. from Eu.)
[+][+] Sepals conspicuously dotted and leaves punctate (except n. 13), with acrid juice; style mostly 3-parted, and achene triangular; sheaths bristle-fringed.
13. P. hydropiperoídes, Michx. (Mild Water-Pepper.) Perennial, not acrid; stem smooth (1–3° high), branching; the narrow sheaths hairy; leaves narrowly lanceolate, sometimes oblong; spikes erect, slender, sometimes filiform, often interrupted at base (1–2½´ long); flowers small, flesh-color or nearly white; sepals not dotted; stamens 8; achene sharply triangular, smooth and shining.—Wet places and in shallow water; common, especially southward.
14. P. Hydrópiper, L. (Common Smartweed or Water-Pepper.) Annual, 1–2° high, smooth; leaves narrowly to linear-lanceolate; spikes nodding, usually short or interrupted; flowers mostly greenish; stamens 6; style 2–3-parted; achene dull, minutely striate.—Moist or wet grounds; apparently introduced eastward, but indigenous north and westward. (Eu.)
15. P. àcre, HBK. (Water Smartweed.) Perennial, nearly smooth; stems rooting at the decumbent base, 2–5° high; leaves larger and longer than in the last, taper-pointed; spikes erect; flowers whitish, sometimes flesh-color; stamens 8; style mostly 3-parted; achene smooth and shining.—Wet places; common, especially southward.
§ 3. BISTÓRTA. Glabrous alpine perennials, with thick creeping rootstocks and simple stems; flowers in a spike-like raceme; calyx colored, deeply 5-cleft; stamens 8; styles 3, long.
16. P. vivíparum, L. Smooth, dwarf (4–8´ high), bearing a linear erect spike of flesh-colored flowers (or often little red bulblets in their place); leaves lanceolate.—Alpine summits of N. Eng., shores of L. Superior, and northward. (Eu.)